All verses are quoted from the NASB anything in [square brackets] is added by me for clarity.

"Immediately the Spirit impelled Him [Jesus] to go out into the wilderness. And He was in the wilderness forty days being tempted by Satan; and He was with the wild beasts, and the angels were ministering to Him." Mark 1:12 & 13

Jesus' audience is Satan, who already believes in the existence of God etc...

"Then Jesus was led up by the Spirit into the wilderness to be tempted by the devil. And after He had fasted forty days and forty nights, He then became hungry. And the tempter came and said to Him, `If You are the Son of God, command that these stones become bread.' But He answered and said, "It is written, `MAN SHALL NOT LIVE ON BREAD ALONE, BUT ON EVERY WORD THAT PROCEEDS OUT OF THE MOUTH OF GOD.' " Matthew 4:1-4

Problem - Jesus has been led by the Spirit into the wilderness. So it is God's will that Jesus be there. Then Satan tries to get Jesus to do something to break His trust in God. That is, Satan is saying - `Even though God has led you here, He will not provide for your needs, so do it yourself.'

Jesus' solution - Quote scripture (remember Satan doesn't have to be 'convinced' that it is the word of God, that is a 'given').

"All the commandments that I [God] am commanding you today you [Israel] shall be careful to do, that you may live and multiply, and go in and possess the land which the LORD swore to give to your forefathers. You shall remember all the way which the LORD your God has led you in the wilderness these forty years, that He might humble you, testing you, to know what was in your heart, whether you would keep His commandments or not. He humbled you and let you be hungry, and fed you with manna which you did not know, nor did your fathers know, that He might make you understand that man does not live by bread alone, but man lives by everything that proceeds out of the mouth of the LORD." Deuteronomy 8:1-3

ok, this is the passage of scripture that Jesus quoted to the devil (or the small bit at the end). And we can see that the situation is similar -

Israel was led into the desert by God's leading, as was Jesus. Jesus knew that God provided for Israel in the wilderness and He knew that God would provide for Him too.